1. Field of the Invention
The present invention relates to a method for manufacturing a crossbeam or slat for a heddle frame of a loom, as well as a crossbeam obtained by this method, this crossbeam having at least one support section and one heddle-support rod or bar affixed to this section along a junction zone.
2. Discussion of Background Information
Heddle frames are well known in the textile industry and are mainly used in looms. Each heddle frame constitutes a rectangular structure arranged to hold the loom heddles. To this end, this rectangular structure conventionally has an upper crossbeam formed of a support section affixed to an upper heddle-support rod, a lower crossbeam formed of a support section affixed to a lower heddle-support rod, and two lateral posts assembled to the ends of the crossbeams to form the frame. The main function of support sections is to bring the rigidity that the heddle-support rods do not have, and these support sections include, as known, a cross-section that is larger than that of the heddle-support rods. Furthermore, in order to guarantee the correct functioning of the loom heddles and their sliding over the entire length of the frame, the heddle-support rods must necessarily be linear and parallel to each other with an accuracy of approximately + or −0.3 mm. It is noted that each loom heddle is constituted of a metal blade provided at its ends with a loop so that it can be mounted on the heddle-support rods, with an operational clearance, and with an eyelet in its center to hold and guide a warp thread. Therefore, there are as many loom heddles as there are warp threads, these loom heddles being distributed, for example, over two heddle frames. On the loom, the heddle frames are put in a reciprocal vertical movement by an adapted driving mechanism. For instance, for a speed of 1200 strokes per minute, each heddle frame is moved at a speed of 600 cycles per minute. The constant increase in weaving speeds has brought about new mechanical behaviors and technical difficulties for heddle frames as well as for loom heddles.
Currently, the support sections are essentially made of aluminum alloy, and the heddle-support rods are usually made of stainless steel and attached to the support sections by means of rivets in order to obtain a rigid assembly. The use of support sections made of aluminum alloy by extrusion or wiredrawing is an advantageous solution since it allows making, at reasonable cost, support sections having a reduced weight and a very good straightness. Also, the possible lack of straightness can be easily corrected by a mechanical straightening operation that is made possible due to the specific mechanical properties of the metal alloys. This straightness then allows using the aluminum support section as a reference for attaching the heddle-support rod thereto with rivets, making it straight. Indeed, this heddle-support rod is not necessarily itself linear, due to its low rigidity.
Nevertheless, this type of widely used heddle frame has modest performances in terms of rigidity, and low resistance to mechanical fatigue. These drawbacks are amplified with the increase in weaving speeds. In addition, the assembly of the heddle-support rods on the support sections by riveting generates concentrations of harmful stresses that can prematurely rupture the heddle frames due to substantial alternative dynamic stress.
An attempt has been made to overcome this drawback by incorporating stiffeners made of carbon fibers in the support sections, and by assembling the heddle-support rod by nesting in a groove provided on each support section, as described in Patent U.S. Pat. No. 4,913,194. However, this type of embodiment is complex and very expensive given the number and diversity of the parts to be assembled.
Another solution is to obtain support sections entirely made of composite materials, for example, by pultrusion of thermoset resins incorporating carbon fibers or glass fibers, and to attach the heddle-support rods by gluing. The composite materials have numerous advantages:                in terms of lightness, they substantially reduce the mass and inertia of the frame, thus improving its dynamic behavior, and        in terms of rigidity in traction and in compression, they increase its resistance to mechanical fatigue well beyond that of aluminum alloys.        
Nonetheless, the performances in terms of straightness are relatively poor. For example, the average deflection of this type of section is approximately 1 mm per 1 meter of length. Knowing that in the field of heddle frames, the support sections can measure up to 4.2 meters, the possible deflection can reach approximately 4 mm. In addition, these composite materials allow no straightening, given that the resins are thermoset and therefore very rigid and irreversible. Using this type of support section implies a rigorous selection of support sections having an acceptable straightness in order to make a consistent heddle-support frame and, consequently, high costs given the substantial waste that it causes.